KR101093712B1 - Negative active material for lithium secondary battery, method of preparing the same, and lithium secondary battery comprising the same - Google Patents

Abstract

The present invention relates to a negative electrode active material for a lithium secondary battery, a method of manufacturing the same, and a lithium secondary battery including the same, wherein the negative electrode active material for a lithium secondary battery has a tap density of 1.2 to 2.2 g / cc lithium titanium oxide (Li ₄ Ti ₅ O ₁₂ ), wherein the lithium titanium oxide is prepared by mechano-chemical treatment and heat treatment at a low temperature of 650 ~ 775 ℃.

According to the present invention, a lithium titanium oxide having a high crystallinity and a tap density can be obtained through a mechanochemical method using a simple and low-cost solid phase method. Can be.

Lithium secondary battery, negative electrode, negative electrode active material, lithium titanium oxide, mechano-chemical treatment

Description

A negative active material for a lithium secondary battery, a method of manufacturing the same, and a lithium secondary battery including the same TECHNICAL FIELD

The present invention relates to a negative electrode active material for a lithium secondary battery, a method for manufacturing the same, and a lithium secondary battery including the same. More particularly, the anode active material for a secondary battery having an excellent electrochemical reaction and a high energy density per volume, and a method for manufacturing the same It relates to a lithium secondary battery.

Lithium secondary battery which attracts attention as power source of recent portable small electronic device

It is a battery which shows a high energy density by showing the discharge voltage 2 times higher than the battery using the conventional aqueous alkali solution using an organic electrolyte solution.

As a cathode active material of a lithium secondary battery, an oxide made of lithium and a transition metal having a structure capable of intercalating lithium, such as LiCoO ₂ , LiMn ₂ O ₄ , and LiNi _1-x Co _x O ₂ (0 <x <1) This is mainly used.

As a negative electrode active material of a lithium secondary battery, various types of carbon-based materials including artificial graphite, natural graphite, and hard carbon capable of inserting / removing lithium have been applied. In the carbon-based material, graphite has a low discharge potential of about 0.2 V compared to lithium, and thus, a lithium secondary battery using a material having a low discharge potential relative to lithium as a negative electrode has a high discharge potential of 3.6 V and excellent energy density. Has

Since the graphite negative electrode active material also has a relatively excellent reversibility, it is now widely used as a power source for portable small electronic devices in view of the long life of the lithium secondary battery.

However, medium and large power supplies such as power tools, automotive power supplies (HEVs and EVs), uninterruptible power supplies (UPS), stationary power systems, etc. There is a need for a negative electrode material that requires charging, longevity, and safety.

In order to solve this problem, a cathode using an oxide has recently been developed. For example, US Pat. Nos. 5,545,468 and 6,645,673 disclose lithium titanium oxide as a negative electrode active material.

In such a conventional method of manufacturing lithium titanium oxide, wet methods (sol-gel method, hydrothermal synthesis, etc.) and solid phase methods are used to obtain lithium titanium oxide having a spinel structure.

When the solid phase method is used, the manufacturing process cost can be reduced compared to the wet method, and the solid phase method is mainly used. However, in the low temperature heat treatment, unreacted titanium dioxide remains, and by-products are generated when the high temperature heat treatment is performed. The particle diameter of the produced lithium titanium oxide is greatly increased, so that deterioration of physical properties is inevitable.

In addition, the titanium oxide formed by the conventional synthetic methods is a porous aggregate composed of nanoparticles is very low, resulting in a low energy density per volume.

One embodiment of the present invention is to provide a negative electrode active material for lithium secondary batteries having excellent electrochemical reaction and high energy density per volume.

Another embodiment of the present invention is to provide a method for producing the negative electrode active material.

Another embodiment of the present invention is to provide a negative electrode including the negative electrode active material.

Another embodiment of the present invention is to provide a lithium secondary battery including the negative electrode.

However, technical problems to be achieved by the present invention are not limited to the above-mentioned problems, and other technical problems will be clearly understood by those skilled in the art from the following description.

An embodiment of the present invention includes a lithium titanium oxide represented by the following Chemical Formula 1, and provides a negative electrode active material for a lithium secondary battery having a tap density of 1.2 to 2.2 g / cc.

Another embodiment of the present invention comprises the steps of mixing a titanium source and a lithium source by a mechano-chemical method (mechano-chemical) to prepare a lithium titanium oxide precursor represented by the formula (1); Grinding the lithium titanium oxide precursor; And heat-treating the pulverized lithium titanium oxide precursor at a temperature of 650 to 775 ° C. to provide a method of manufacturing a negative electrode active material for a lithium secondary battery.

Another embodiment of the present invention is a negative electrode active material containing lithium titanium oxide represented by the following formula (1) having a tap density of 1.2 to 2.0 g / cc 75 to 98% by weight, 1 to 15% by weight of the conductive material, and binder 1 to It provides a negative electrode for a lithium secondary battery comprising 10% by weight.

[Formula 1]

Li _x Ti _y O _z

(Wherein

0.1≤x≤4, 1≤y≤5, 2≤z≤12.)

Another embodiment of the invention the negative electrode of the present invention; A positive electrode including a positive electrode active material; And it provides a lithium secondary battery comprising an electrolyte.

Other specific details of embodiments of the present invention are included in the following detailed description.

According to the present invention, a lithium titanium oxide having a high crystallinity and a tap density can be obtained through a mechanochemical method using a simple and low-cost solid phase method. Can be.

Hereinafter, embodiments of the present invention will be described in detail. However, this is presented as an example, by which the present invention is not limited and the present invention is defined only by the scope of the claims to be described later.

One embodiment of the present invention provides a lithium titanium oxide represented by the following formula (1) as a negative electrode active material for a lithium secondary battery.

[Formula 1]

Li _x Ti _y O _z

(Wherein

0.1≤x≤4, 1≤y≤5, 2≤z≤12.)

The lithium titanium oxide according to the present invention is preferably Li ₄ Ti ₅ O ₁₂ .

In addition, the lithium titanium oxide of the present invention preferably has a tap density of 1.2 g / cc or more, more preferably 1.2 to 2.2 g / cc, and most preferably 1.5 to 2.0 g / cc. When the tap density of the lithium titanium oxide is 1.2 g / cc or more, an electrode having excellent electrochemical reaction and high energy density per volume can be obtained.

In addition, the particle size (primary particle size) of the lithium titanium oxide is preferably 20 to 700 nm, more preferably 200 to 500 nm. When the lithium titanium oxide particle diameter is 20 to 700 nm, it has a high tap density. In addition, by using a small amount of a conductive material and a binder it is easy to manufacture slurry and electrode plate production and excellent electrochemical properties.

The lithium titanium oxide of the present invention is a solid phase method by uniformly dispersing the lithium compound in the titanium compound of the nanoparticles by a mechano-chemical method to induce a diffusion reaction of lithium in the titanium compound, and then heat treatment at low temperature It is prepared by, thereby obtaining a lithium titanium oxide having a high density and high performance.

The manufacturing method of the negative electrode active material of this invention is as follows.

First, a titanium source and a lithium source are mixed by a mechanochemical method to prepare a lithium titanium oxide precursor.

In this case, the titanium source may be selected from the group consisting of titanium dioxide (TiO ₂ ), solid titanium chloride, solid titanium sulfide, and solid titanium hydroxide.

The titanium dioxide (TiO ₂ ) is a group consisting of an anatase crystal phase, a rutile crystal phase, anatase crystal phase and a rutile crystal phase, a brookite crystal phase and a TiO ₂ -B crystal phase, and combinations thereof The one selected from may be used. Among them, preferably, an anatase crystalline phase or a mixture of an anatase crystalline phase and a rutile crystalline phase may be used.

When the titanium dioxide (TiO ₂ ) is a mixture of the anatase crystal phase and the rutile crystal phase, it is preferable that the anatase crystal phase is mixed at 60 wt% or more.

In addition, when the titanium dioxide (TiO ₂ ) is a mixture of a brookite (brookite) and a TiO ₂ -B (nanowire or nanotube) crystal phase can be synthesized lithium titanium oxide by low temperature reaction.

In addition, the titanium source preferably has a particle diameter of 200 nm or less, more preferably 50 nm or less, and most preferably 5 to 50 nm. When the particle diameter of the titanium source is 50 nm or less, the pretreatment and heat treatment time by mechanochemical can be shortened, and low temperature heat treatment can be performed to synthesize lithium titanium oxide having a small particle size of 500 nm or less.

In addition, the titanium source may be a mixture of particles having different particle diameters or particles having a particle size distribution of bimodal.

In the case of a titanium source formed by mixing particles having different particle diameters, the diameter ratio of the small particles to the large particles is preferably 0.1 to 0.4, and the volume ratio and the weight ratio of the small particles to the large particles are preferably 0.15 to 0.3, respectively. When mechanochemical treatment is performed with the titanium source having the diameter ratio of 0.1 to 0.4 or the titanium source having the volume ratio and the weight ratio of 0.15 to 0.3, the two particles are mixed and dispersed to obtain a lithium titanium oxide in which the particles are densely arranged. .

The lithium source is LiOH, LiOH, H₂Lithium hydroxide, such as O, lithium carbonate (Li₂CO₃), LiOOCCH₃, LiOOCCH₃2H₂One selected from the group consisting of lithium acetate such as O, a solid lithium source, and a combination thereof can be used.

The mechanochemical method according to the present invention can be carried out by adjusting the operating conditions such as reaction temperature, time, rotational speed, the amount of reactants. In particular, it is preferably carried out at the reactor temperature of 150 to 500 ℃, time 20 to 60 minutes, and operating conditions of the rotor speed of 5 to 25 m / s. When carried out in each of the above conditions range can be easily adjusted to the high tap density of the lithium titanium oxide according to the present invention, can lower the heat treatment temperature and shorten the heat treatment time can increase the throughput per unit process.

The lithium titanium oxide precursor consisting of the agglomerated phase of the nanoparticles obtained through the mechanochemical method as described above is crushed and sieved or classified to the size of the secondary particle diameter of the desired agglomerated phase.

The secondary particle diameter of the desired aggregated phase is preferably 5 to 50 mm, more preferably 10 to 20 mm.

Thereafter, the lithium titanium oxide precursor is heat-treated to prepare lithium titanium oxide, which is the anode active material of the present invention.

The heat treatment is preferably performed at a low temperature of 650 to 775 ° C, more preferably at a temperature of 700 to 725 ° C. When the heat treatment is performed at 650 to 775 ° C., lithium titanium oxide having a nano-sized particle diameter can be obtained, and impurities of unreacted titanium dioxide are hardly shown. As a result, an electrode having excellent electrochemical reaction can be obtained.

The particle diameter of the lithium titanium oxide prepared by the mechanochemical method and low temperature heat treatment is preferably 20 to 700 nm, more preferably 200 to 500 nm. When the lithium titanium oxide particle diameter is 20 to 700 nm, it has a high tap density. In addition, by using a small amount of a conductive material and a binder it is easy to manufacture slurry and electrode plate production and excellent electrochemical properties.

In addition, the lithium titanium oxide has a dense structure between primary particles, the tap density of the lithium titanium oxide is preferably 1.2 g / cc or more, more preferably 1.2 to 2.2 g / cc, most preferably 1.5 Preferably from 2.0 g / cc. When the tap density of the lithium titanium oxide is 1.2 g / cc or more, it is possible to obtain an electrode having excellent electrochemical reaction and a high energy density per volume.

In the present invention, a lithium titanium oxide having a high crystallinity and a high crystallinity can be obtained even by a simple solid phase process. In addition, a lithium titanium oxide having a high tap density can be obtained due to the close spacing between nanoparticles. An electrode having a high energy density can be produced.

The present invention also provides a negative electrode comprising a negative electrode active material prepared by the above method.

The negative electrode includes the negative electrode active material, the conductive material, and the binder of the present invention. In particular, the negative electrode active material is preferably mixed with 75 to 98% by weight, 1 to 15% by weight of the conductive material, and 1 to 10% by weight of the binder, more preferably 80 to 94% by weight of the negative electrode active material, 3 to 10 It is preferable that the mixture is made up of 3% by weight and 3 to 10% by weight of the binder.

When the negative electrode is mixed with 75 to 98 wt% of the negative electrode active material, 1 to 15 wt% of the conductive material, and 1 to 10 wt% of the binder, an electrode having a high energy density per volume may be manufactured.

In addition, the content of the conductive material may be differently adjusted according to the output of the battery used in the negative electrode of the present invention. Specifically, when the output of the battery is less than 20C rate (current capacity rate per hour, target capacity (mAh) 1 /). When released in 20 hours (3 minutes) or more), the content of the conductive material in the negative electrode active material layer is preferably 5% by weight or less, preferably 1 to 4% by weight. In addition, when the output of the battery is 20C rate or more (when releasing the current capacity per hour, the desired capacity (mAh) in 1/20 hours (3 minutes) or less), the content of the conductive material is 6 to 15% by weight, preferably 7 It is preferred to use from 12% by weight.

In addition, when the output of the battery is less than 20C rate, the content of the negative electrode active material in the negative electrode active material layer is preferably used at 92 to 98% by weight, preferably 94 to 96% by weight. The content of the negative electrode active material is preferably 75 to 86% by weight, preferably 80 to 86% by weight.

Specifically, the negative electrode of the present invention may be prepared by mixing the negative electrode active material, the conductive material, the binder, and an organic solvent to prepare a negative electrode active material composition, and then applying the negative electrode active material composition to a current collector.

The conductive material may be selected from the group consisting of natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, hard carbon, soft carbon, carbon fiber, copper, nickel, aluminum, silver metal powder and metal fiber. have.

In addition, the binder is polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymer containing ethylene oxide, polyvinylpyrrolidone, polyurethane , Polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin and nylon may be used.

In addition, the current collector may be selected from the group consisting of copper foil, aluminum foil, nickel foil, stainless steel foil, titanium foil, nickel foam (foam), a copper foam and a polymer substrate coated with a conductive metal. Also aluminum or alloys of copper and aluminum can be used, preferably aluminum with low cost and light weight properties.

It is preferable that the negative electrode of the present invention prepared as described above has a high density of 1.8 g / cc or more, more preferably 2.0 g / cc or more, and most preferably 2.0 to 2.4 g / cc. When the mixture density of the negative electrode is 1.8 g / cc or more, an electrode having a high energy density per volume can be formed and the electrochemical reaction is excellent.

In this case, the mixture density means the density of the current collector and the negative electrode active material layer formed on the current collector.

In addition, it is possible to adjust the loading level range according to the output range to be used. Specifically, when the use output is 20C rate or less, it is manufactured with an electrode of 1.5 mAh / cm ² or more, and when the use output is 20C rate or more, 1.5 mAh / to fabricate the electrodes of ² cm or less.

The present invention also provides a lithium secondary battery comprising the negative electrode.

The lithium secondary battery comprises a negative electrode, a positive electrode and an electrolyte prepared by the method of the present invention.

The positive electrode includes a current collector and a cathode active material layer formed on the current collector. As the positive electrode active material, a compound (lithiated intercalation compound) capable of reversible intercalation and deintercalation of lithium may be used. Specifically, at least one of a complex oxide of a metal and lithium selected from cobalt, manganese, nickel, and combinations thereof may be used, and specific examples thereof may be a compound represented by any one of the following formulas. Li _a A _1-b B _b D ₂ (wherein 0.90 ≦ a ≦ 1.8, and 0 ≦ b ≦ 0.5); Li _a E _1-b B _b 0 _2-c D _c (wherein 0.90 ≦ a ≦ 1.8, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05); LiE _2-b B _b 0 _4-c D _c (wherein 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05); Li _a Ni _1-bc Co _b B _c D _α (wherein 0.90 ≦ a ≦ 1.8, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05, and 0 <α ≦ 2); Li _a Ni _1-bc Co _b B _c 0 _2-α F _α (wherein 0.90 ≦ a ≦ 1.8, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05, and 0 <α <2); Li _a Ni _1-bc Co _b B _c O _2-α F ₂ (wherein 0.90 ≦ a ≦ 1.8, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05, and 0 <α <2); Li _a Ni _1-bc Mn _b B _c D _α (wherein 0.90 ≦ a ≦ 1.8, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05, and 0 <α ≦ 2); Li _a Ni _1-bc Mn _b B _c O _2-α F _α (wherein 0.90 ≦ a ≦ 1.8, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05, and 0 <α <2); Li _a Ni _1-bc Mn _b B _c O _2-α F ₂ (wherein 0.90 ≦ a ≦ 1.8, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05, and 0 <α <2); Li _a Ni _b E _c G _d O ₂ (wherein 0.90 ≦ a ≦ 1.8, 0 ≦ b ≦ 0.9, 0 ≦ c ≦ 0.5, and 0.001 ≦ d ≦ 0.1); Li _a Ni _b Co _c Mn _d GeO ₂ wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0 ≤ d ≤ 0.5, and 0.001 ≤ e ≤ 0.1; Li _a NiG _b O ₂ (wherein 0.90 ≦ a ≦ 1.8 and 0.001 ≦ b ≦ 0.1); Li _a CoG _b O ₂ (wherein 0.90 ≦ a ≦ 1.8 and 0.001 ≦ b ≦ 0.1); Li _a MnG _b O ₂ (wherein 0.90 ≦ a ≦ 1.8 and 0.001 ≦ b ≦ 0.1); Li _a Mn ₂ G _b O ₄ (wherein 0.90 ≦ a ≦ 1.8 and 0.001 ≦ b ≦ 0.1); QO ₂ ; QS ₂ ; LiQS ₂ ; V ₂ O ₅ ; LiV ₂ O ₅ ; LiIO ₂ ; LiNiVO ₄ ; Li _(3-f) J ₂ (PO ₄ ) ₃ (0 ≦ f ≦ 2); Li _(3-f) Fe ₂ (PO ₄ ) ₃ (0 ≦ f ≦ 2); LiFePO ₄

In the above formula, A is selected from the group consisting of Ni, Co, Mn, and combinations thereof; B is selected from the group consisting of Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements and combinations thereof; D is selected from the group consisting of O, F, S, P, and combinations thereof; E is selected from the group consisting of Co, Mn, and combinations thereof; F is selected from the group consisting of F, S, P, and combinations thereof; G is selected from the group consisting of Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, and combinations thereof; Q is selected from the group consisting of Ti, Mo, Mn, and combinations thereof; I is selected from the group consisting of Cr, V, Fe, Sc, Y, and combinations thereof; J is selected from the group consisting of V, Cr, Mn, Co, Ni, Cu, and combinations thereof.

Of course, a compound having a coating layer on the surface of the compound may be used, or a compound having a coating layer may be mixed with the compound. The coating layer may include at least one coating element compound selected from the group consisting of oxides of the coating elements, hydroxides, oxy hydroxides of the coating elements, oxy carbonates of the coating elements and hydroxycarbonates of the coating elements. The compounds constituting these coating layers may be amorphous or crystalline. As the coating element included in the coating layer, Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr or a mixture thereof may be used. The coating layer forming process may use any coating method as long as it does not adversely affect the physical properties of the positive electrode active material by using such elements in the compound (for example, spray coating, dipping, etc.). Details that will be well understood by those in the field will be omitted.

The cathode active material layer also includes a binder and a conductive material.

The binder adheres positively to the positive electrode active material particles, and also serves to adhere the positive electrode active material to the current collector well, and examples thereof include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, and polyvinyl. Chloride, carboxylated polyvinylchloride, polyvinylfluoride, polymer comprising ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene- Butadiene rubber, acrylic styrene-butadiene rubber, epoxy resin, nylon and the like can be used, but is not limited thereto.

The conductive material is used to impart conductivity to an electrode, and any battery can be used as long as it is an electronic conductive material without causing chemical change in the battery. For example, natural graphite, artificial graphite, carbon black, acetylene black, and ketjen. Metal powder, metal fiber, etc., such as black, carbon fiber, copper, nickel, aluminum, silver, etc. can be used, and 1 type (s) or 1 or more types can be mixed and conductive materials, such as a polyphenylene derivative, can be used.

As the current collector, Al may be used, but the present invention is not limited thereto.

The positive electrode is prepared by mixing an active material, a conductive material and a binder in a solvent to prepare an active material composition, and applying the composition to a current collector. The method of manufacturing the electrode is well known in the art, and therefore, a detailed description thereof will be omitted herein. N-methylpyrrolidone may be used as the solvent, but is not limited thereto.

In the nonaqueous electrolyte secondary battery of the present invention, the nonaqueous electrolyte includes a nonaqueous organic solvent and a lithium salt.

The non-aqueous organic solvent serves as a medium through which ions involved in the electrochemical reaction of the battery can move.

As the non-aqueous organic solvent, a carbonate-based, ester-based, ether-based, ketone-based, alcohol-based or aprotic solvent may be used. Examples of the carbonate solvent include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), methylethyl carbonate (MEC), and ethylene carbonate ( EC), propylene carbonate (PC), butylene carbonate (BC) and the like can be used, and the ester solvent is methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate , γ-butyrolactone, decanolide, valerolactone, mevalonolactone, caprolactone, and the like may be used. Examples of the ether solvent include dibutyl ether, tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, and tetrahydrofuran. As the ketone solvent, cyclohexanone may be used have. In addition, ethyl alcohol, isopropyl alcohol, etc. may be used as the alcohol solvent, and the aprotic solvent may be R-CN (R is a straight-chain, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms. Amides such as nitriles, dimethylformamide, and dioxolanes such as 1,3-dioxolane, and sulfolanes such as 1,3-dioxolane.

The non-aqueous organic solvent may be used alone or in admixture of one or more. If the non-aqueous organic solvent is used in combination, the mixing ratio may be appropriately adjusted according to the desired cell performance. .

In addition, in the case of the carbonate solvent, it is preferable to use a mixture of cyclic carbonate and chain carbonate. In this case, the cyclic carbonate and the chain carbonate may be mixed and used in a volume ratio of 1: 1 to 1: 9, so that the performance of the electrolyte may be excellent.

The non-aqueous organic solvent of the present invention may further comprise an aromatic hydrocarbon-based organic solvent in the carbonate-based solvent. In this case, the carbonate-based solvent and the aromatic hydrocarbon-based organic solvent may be mixed in a volume ratio of 1: 1 to 30: 1.

As the aromatic hydrocarbon organic solvent, an aromatic hydrocarbon compound of Formula 2 may be used.

[Formula 2]

(In Formula 2, R ₁ to R ₆ are each independently selected from the group consisting of hydrogen, halogen, alkyl group having 1 to 10 carbon atoms, haloalkyl group, and combinations thereof.)

The aromatic hydrocarbon organic solvent is benzene, fluorobenzene, 1,2-difluorobenzene, 1,3-difluorobenzene, 1,4-difluorobenzene, 1,2,3-trifluorobenzene , 1,2,4-trifluorobenzene, chlorobenzene, 1,2-dichlorobenzene, 1,3-dichlorobenzene, 1,4-dichlorobenzene, 1,2,3-trichlorobenzene, 1,2, 4-trichlorobenzene, iodobenzene, 1,2-dioodobenzene, 1,3-dioodobenzene, 1,4-dioiobenzene, 1,2,3-triiodobenzene, 1,2,4 -Triiodobenzene, toluene, fluorotoluene, 1,2-difluorotoluene, 1,3-difluorotoluene, 1,4-difluorotoluene, 1,2,3-trifluorotoluene, 1,2,4-trifluorotoluene, chlorotoluene, 1,2-dichlorotoluene, 1,3-dichlorotoluene, 1,4-dichlorotoluene, 1,2,3-trichlorotoluene, 1,2,4 -Trichlorotoluene, iodotoluene, 1,2-dioodotoluene, 1,3-dioodotoluene, 1,4-diaodotol Yen, it is 1,2,3-tree-iodo toluene, 1,2,4-iodo toluene, xylene, and selected from the group consisting of.

The non-aqueous electrolyte may further include vinylene carbonate or an ethylene carbonate-based compound of Formula 3 to improve battery life.

(3)

(In Formula 3, R ₇ and R ₈ are each independently selected from the group consisting of hydrogen, a halogen group, a cyano group (CN), a nitro group (NO ₂ ) and a fluorinated C1-5 alkyl group, wherein R At least one of ₇ and R ₈ is selected from the group consisting of a halogen group, a cyano group (CN), a nitro group (NO ₂ ) and a fluorinated C1-5 alkyl group, provided that R ₇ and R ₈ are not all hydrogen .)

Representative examples of the ethylene carbonate-based compound include diethylene carbonate, diethylene carbonate, dibromoethylene carbonate, nitroethylene carbonate, cyanoethylene carbonate, fluoroethylene carbonate, and the like, such as difluoroethylene carbonate, chloroethylene carbonate, dichloroethylene carbonate, . When such a life improving additive is further used, its amount can be appropriately adjusted.

The lithium salt is dissolved in an organic solvent to act as a source of lithium ions in the cell to enable operation of a basic lithium secondary battery and to promote the movement of lithium ions between the anode and the cathode. Representative examples of such lithium salts are LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , LiN (SO ₂ C ₂ F ₅ ) ₂ , Li (CF ₃ SO ₂ ) ₂ N, LiN (SO ₃ C ₂ F ₅ ) ₂ , LiC ₄ F ₉ SO ₃ , LiClO ₄ , LiAlO ₂ , LiAlCl ₄ , LiN (C _x F _{2x + 1} SO ₂ ) (C _y F _{2y + 1} SO ₂ ), where x and y are natural numbers, LiCl, One or more selected from the group consisting of LiI and LiB (C ₂ O ₄ ) ₂ (lithium bis (oxalato) borate (LiBOB)) are included as supporting electrolytic salts. It is preferable to use in the range of 0.1 to 2.0 M. When the concentration of the lithium salt is included in the above range, since the electrolyte has an appropriate conductivity and viscosity, excellent electrolyte performance can be exhibited, and lithium ions can be effectively moved.

Depending on the type of the lithium secondary battery, a separator may exist between the positive electrode and the negative electrode. The separator may be a polyethylene / polypropylene double layer separator, a polyethylene / polypropylene / polyethylene triple layer separator, a polypropylene / polyethylene / poly It is needless to say that a mixed multilayer film such as a propylene three-layer separator and the like can be used.

Hereinafter, preferred embodiments of the present invention will be described. However, the following examples are only preferred embodiments of the present invention, and the present invention is not limited by the following examples.

[Example]

<Negative Electrode Active Material Manufacturing>

Example 1

About 80% by weight of the anatase crystal phase and about 20% by weight of the rutile crystal phase were mixed with titanium dioxide (TiO ₂ ) and LiOH having an average particle diameter of 30 nm by a mechano-chemical treatment to obtain lithium titanium oxide (Li _4). Ti ₅ O ₁₂ ) precursor was prepared.

The mechanochemical method was carried out using a mechanofusion system (Hosokawa micron) to adjust the operating conditions of the reaction temperature 150 ℃, 20 minutes and the rotor speed of 10 m / s. The tap density was measured in a tap density meter (Seishin, Multi tester MT-1000) according to the ASTM B527 method.

Thereafter, the lithium titanium oxide precursor was pulverized, and then heat treated at a temperature of 700 ° C., a heating rate of 3 ° C./min, and a holding time of 6 hr to prepare a negative electrode active material of lithium titanium oxide. The particle diameter of the prepared lithium titanium oxide was 500 nm, the tap density was 1.2 g / cc.

The thermogravimetric analysis (TGA) result of the lithium titanium oxide precursor according to Example 1 is shown in FIG. 1. As shown in Figure 1, the lithium titanium oxide precursor can be confirmed that the weight reduction proceeds to 650 ℃ proceeds the crystallization of lithium titanium oxide at a higher temperature.

Example 2

In Example 1, the reaction was carried out in the same manner as in Example 1, except that the operating conditions of the reaction temperature of 300 ° C., time 40 minutes, and rotating body speed of 15 m / s in the mechanochemical method were adjusted. The particle size of the prepared lithium titanium oxide was 500 nm, the tap density was 1.6 g / cc.

Example 3

In Example 1, the reaction was carried out in the same manner as in Example 1, except that the operating conditions of the reaction temperature of 500 ° C., time 40 minutes, and the rotor speed of 20 m / s in the mechanochemical method were adjusted. The particle diameter of the prepared lithium titanium oxide was 500 nm, the tap density was 2.0 g / cc.

Comparative Example 1

It was carried out in the same manner as in Example 1 except that titanium dioxide (TiO ₂ ) and LiOH were simply mixed without mechano-chemical treatment. The particle diameter of the prepared lithium titanium oxide was 400 nm, the tap density was 0.8 g / cc.

Comparative Example 2

In Example 1, a lithium titanium oxide precursor was prepared by adjusting an operating condition of a reaction temperature of 300 ° C., a time of 40 minutes, and a rotating body speed of 15 m / s in the mechanochemical method. The lithium titanium oxide precursor was prepared at a temperature of 600 ° C., The same process as in Example 1 was carried out except that heat treatment was performed under a heating rate of 3 ° C./min and a holding time of 12 hr. The particle size of the prepared lithium titanium oxide was 300 nm, the tap density was 1.1 g / cc.

Comparative Example 3

In Example 1, a lithium titanium oxide precursor was prepared by adjusting an operating condition of a reaction temperature of 300 ° C., a time of 40 minutes, and a rotating body speed of 15 m / s in the mechanochemical method. The lithium titanium oxide precursor was prepared at a temperature of 800 ° C., The same process as in Example 1 was carried out except that heat treatment was performed under a heating rate of 3 ° C./min and a holding time of 6 hr. The particle size of the prepared lithium titanium oxide was 1000 nm, the tap density was 2.2 g / cc.

Comparative Example 4

In Example 1, a lithium titanium oxide precursor was prepared by adjusting an operating condition of a reaction temperature of 300 ° C., a time of 40 minutes, and a rotating body speed of 15 m / s in the mechanochemical method. The same process as in Example 1 was carried out except that heat treatment was performed under a heating rate of 3 ° C./min and a holding time of 6 hr. The particle size of the prepared lithium titanium oxide was 2000 nm, the tap density was 2.2 g / cc.

The tap densities of the negative electrode active materials prepared according to Examples 1 to 3 and Comparative Examples 1 to 4 are shown in Table 1 below.

[Table 1]

Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Mechanochemical Method ○ ○ ○ X ○ ○ ○ Heat treatment temperature (℃) 700 700 700 700 600 800 900 Tap Density of Lithium Titanium Oxide (g / cc) 1.2 1.6 2.0 0.8 1.1 2.2 2.2 Particle Size of Lithium Titanium Oxide (nm) 500 500 500 400 300 1000 2000

Experimental Example 1 X-ray Diffraction (XRD) Analysis of Lithium Titanium Oxide

X-ray diffraction (XRD) analysis results of the lithium titanium oxide prepared according to Example 1 and Comparative Examples 2 to 4 are shown in FIG. 2.

As shown in FIG. 2, in the case of lithium titanium oxide heat-treated at a temperature of 700 ° C. according to Example 1, in the case of lithium titanium oxide heat-treated at a temperature of 800 ° C. according to Comparative Example 3, and according to Comparative Example 4 In the case of lithium titanium oxide heat-treated at a temperature of 900 ℃, it can be seen that the impurity peaks hardly appear and coincide with the characteristic peaks of lithium titanium oxide.

On the other hand, in the case of lithium titanium oxide heat-treated at a temperature of 600 ℃ according to Comparative Example 2 it can be seen that there is a significant presence of unreacted titanium dioxide and other lithium titanium oxide.

Experimental Example 2: Scanning Electron Microscope (SEM) Measurement of Lithium Titanium Oxide

Scanning electron microscope (SEM) photographs of lithium titanium oxide prepared according to Example 1 and Comparative Examples 2 to 4 are shown in FIGS. 3A to 3D.

As shown in FIG. 3A, in the case of lithium titanium oxide heat-treated at a temperature of 700 ° C. according to Example 1, it may be confirmed that a particle diameter is obtained at a level of 500 nm.

On the other hand, in the case of lithium titanium oxide heat-treated at a temperature of 600 ℃ according to Comparative Example 2 it can be seen that a relatively small particle size of 300 nm is obtained.

In addition, in the case of lithium titanium oxide heat-treated at the temperature of 800 ℃ and 900 ℃ according to Comparative Examples 3 and 4 it can be confirmed that the particle diameter is obtained by excessively growing to the level of 1 to 2 ㎛.

<The cathode and the lithium secondary battery including the same>

Example 4

A negative electrode active material slurry was prepared by mixing 80% by weight of the negative electrode active material prepared according to Example 1, 10% by weight of carbon black, and 10% by weight of polyvinylidene fluoride in N-methyl pyrrolidone. The negative electrode active material slurry was uniformly coated and dried on an aluminum foil having a thickness of 20 μm, and then roll-pressed to prepare a negative electrode. Thus, the mixture density of the negative electrode produced was 1.8 g / cc.

A half cell was produced by a conventional method using Li metal as a counter electrode and using the negative electrode, counter electrode, and electrolyte solution prepared above.

Example 5

Example 4 was carried out in the same manner as in Example 4, except that the negative electrode active material prepared according to Example 2 was used. Thus, the mixture density of the produced negative electrode was 2.0 g / cc.

Example 6

Example 4 was carried out in the same manner as in Example 4, except that the negative electrode active material prepared according to Example 3 was used. Thus, the mixture density of the negative electrode produced was 2.1 g / cc.

Example 7

Example 4 was carried out in the same manner as in Example 4, except that 90% by weight of the negative electrode active material prepared according to Example 3, 5% by weight of the carbon black conductive material, and 5% by weight of the PVdF-based binder were mixed. Thus, the mixture density of the negative electrode produced was 2.4 g / cc.

Comparative Example 5

Example 4 was carried out in the same manner as in Example 4, except that the negative electrode active material prepared according to Comparative Example 1 was used. Thus, the mixture density of the negative electrode produced was 1.5 g / cc.

Comparative Example 6

Example 4 was carried out in the same manner as in Example 4, except that the negative electrode active material prepared according to Comparative Example 2. The mixture density of the negative electrode thus produced was 1.7 g / cc.

Comparative Example 7

Example 4 was carried out in the same manner as in Example 4, except that the negative electrode active material prepared according to Comparative Example 3. The material density of the negative electrode thus produced was 2.2 g / cc.

Comparative Example 8

Example 4 was carried out in the same manner as in Example 4, except that the negative electrode active material prepared according to Comparative Example 4. The material density of the negative electrode thus produced was 2.2 g / cc.

The mixture densities of the negative electrodes prepared according to Examples 4 to 7 and Comparative Examples 5 to 8 are shown in Table 2 below.

TABLE 2

Example 4 Example 5 Example 6 Example 7 Comparative Example 5 Comparative Example 6 Comparative Example 7 Comparative Example 8 Composition Content of Cathode Anode active material
(weight%) 80 80 80 90 80 80 80 80 Conductive material
(weight%) 10 10 10 5 10 10 10 10 bookbinder
(weight%) 10 10 10 5 10 10 10 10 Material density of the negative electrode (g / cc) 1.8 2.0 2.1 2.4 1.5 1.7 2.2 2.2

Experimental Example 3: Measurement of charge and discharge characteristics

The lithium secondary batteries prepared according to Examples 4 to 7 and Comparative Examples 5 to 8 were charged and discharged at 0.5C once to measure electrochemical charge and discharge characteristics.

4 is a graph showing charge and discharge characteristics of lithium titanium oxide prepared at each heat treatment temperature according to Example 1 and Comparative Examples 2 to 4.

As shown in FIG. 4, it can be seen that the electrochemical properties of the lithium titanium oxide prepared by heat treatment at 700 ° C. according to Example 1 are most excellent.

Experimental Example 4 Mixture Level Measurement According to Use Output

For the lithium secondary battery produced according to Example 4, an experiment was conducted to find an appropriate mixture level according to the use output.

5 is a graph showing the remaining capacity and the mixture level according to the use output in the lithium secondary battery according to Example 4.

As shown in FIG. 5, it can be seen that the remaining capacity decreases as the mixture level increases. In particular, it can be seen that the capacity decreases significantly as the usage level increases at 20C rate. Therefore, the output used can be confirmed that the laminated material level is laminated material level is preferably made of 1.5 mAh / cm ² or lower electrode when the production, and the output used as 1.5 mAh / cm ² or more electrodes than 20C rate is less than 20C rate .

Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications and changes can be made within the scope of the claims and the detailed description of the invention and the accompanying drawings. Naturally, it belongs to the scope of the invention.

1 is a graph showing the result of thermogravimetric analysis (TGA) of a lithium titanium oxide precursor according to Example 1 of the present invention.

2 is an X-ray diffraction (XRD) analysis pattern of lithium titanium oxide according to Example 1 and Comparative Examples 2 to 4 of the present invention.

3A to 3D are scanning electron microscope (SEM) photographs of lithium titanium oxide according to Example 1 and Comparative Examples 2 to 4 of the present invention.

4 is a graph showing charge and discharge characteristics of lithium titanium oxide according to Example 1 and Comparative Examples 2 to 4 of the present invention.

5 is a graph showing the retention capacity and the mixture level according to the use output in the lithium secondary battery according to a fourth embodiment of the present invention.

Claims (20)

To include a lithium titanium oxide represented by the formula (1), The tap density of the lithium titanium oxide is 1.2 to 2.2 g / cc and the particle size of the negative electrode active material for a lithium secondary battery is 200 to 500 nm. [Formula 1] Li _x Ti _y O _z (Wherein 0.1≤x≤4, 1≤y≤5, 2≤z≤12.) The method of claim 1, The lithium titanium oxide is Li ₄ Ti ₅ O _{12 It} is a negative electrode active material for a lithium secondary battery. delete Mixing a titanium source and a lithium source by a mechano-chemical method to prepare a lithium titanium oxide precursor represented by Formula 1 below; Grinding the lithium titanium oxide precursor; And And heat treating the pulverized lithium titanium oxide precursor at a temperature of 650 to 775 ° C. to produce lithium titanium oxide, The tap density of the lithium titanium oxide is 1.2 to 2.2 g / cc and the particle size of 200 to 500 nm manufacturing method of the negative electrode active material for a lithium secondary battery. [Formula 1] Li _x Ti _y O _z (Wherein 0.1≤x≤4, 1≤y≤5, 2≤z≤12.) 5. The method of claim 4, The titanium source is selected from the group consisting of titanium dioxide (TiO ₂ ), solid titanium chloride, solid titanium sulfide, and solid titanium acid hydroxide. 5. The method of claim 4, The lithium source is a lithium hydroxide, lithium carbonate, lithium acetate, a solid lithium source and a method for producing a negative electrode active material for a lithium secondary battery that is a combination thereof. 5. The method of claim 4, The lithium titanium oxide is Li ₄ Ti ₅ O _{12 A} method for producing a negative electrode active material for a lithium secondary battery. 5. The method of claim 4, The particle size of the said titanium source is 200 nm or less, The manufacturing method of the negative electrode active material for lithium secondary batteries. The method of claim 5, The titanium dioxide (TiO ₂ ) is a group consisting of an anatase crystal phase, a rutile crystal phase, anatase crystal phase and a rutile crystal phase, a brookite crystal phase and a TiO ₂ -B crystal phase, and combinations thereof Method for producing a negative active material for a lithium secondary battery that is selected from. 5. The method of claim 4, The mechanochemical method is a method for producing a negative electrode active material for a lithium secondary battery that is carried out under the operating conditions of the reactor temperature of 150 to 500 ℃, reaction time of 20 to 60 minutes, and rotor speed of 5 to 25 m / s. delete delete A negative electrode for a lithium secondary battery comprising a negative electrode active material, a conductive material, and a binder including a lithium titanium oxide represented by the following Chemical Formula 1 having a tap density of 1.2 to 2.2 g / cc and a particle diameter of 200 to 500 nm. [Formula 1] Li _x Ti _y O _z (Wherein 0.1≤x≤4, 1≤y≤5, 2≤z≤12.) The method of claim 13, The negative electrode for a lithium secondary battery includes 75 to 98% by weight of the negative electrode active material, 1 to 15% by weight of the conductive material, and 1 to 10% by weight of the binder. The method of claim 13, The lithium titanium oxide is Li ₄ Ti ₅ O _{12 It} is a negative electrode for a lithium secondary battery. delete The method of claim 13, Wherein the conductive material is selected from the group consisting of natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, copper, nickel, aluminum, silver metal powder and metal fiber negative electrode for a lithium secondary battery. The method of claim 13, The binder is polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, polyvinyl chloride, carboxylated polyvinylchloride, polyvinyl fluoride, polymer comprising ethylene oxide, polyvinylpyrrolidone, polyurethane, poly A negative electrode for a lithium secondary battery selected from the group consisting of tetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin and nylon. The method of claim 13, The negative electrode material density of the negative electrode is 1.8 to 2.4 g / cc. A negative electrode prepared according to any one of claims 13 to 15 and 17 to 19; A positive electrode including a positive electrode active material; And Electrolyte Lithium secondary battery comprising a.

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